Crestwood, MO (KSDK) - Grease build-up in a vent is the likely culprit for a smoky fire that firefighters responded to early Friday at a fast food restaurant in southwest St. Louis County.

The call was at the McDonald's restaurant in the 9900 block of Watson Road in Crestwood just after 5:00 a.m.

Smoke was noticied rising from the roof of the building as Crestwood fire officials arrived at the location. The small fire was quickly put out, but ventilating the smoke from the building took the better part of an hour.

The restaurant was closed at the time of the fire, but the business reopened to customers by 9 a.m.

The fire caused no structural damage, but destroyed one piece of equipment that will have to be replaced.